//基于套接字的标准I/O函数
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30
void error_handling(char* message);

int main(int argc, char* argv[])
{
    int serv_sock, clnt_sock;//用于服务端的套接字，用于客户端连接的套接字
    char message[BUF_SIZE];//存储输入的字符串
    int str_len, i;
    
    struct sockaddr_in serv_addr, clnt_addr;
    socklen_t clnt_adr_sz;

    FILE* readfp, *writefp;//用于读、写的文件指针

    if(argc != 2)
    {
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }

    //socket()创建socket
    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if(serv_sock == -1)
        error_handling("socket() error\n");

    //bind()分配ip和端口
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    if(bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
        error_handling("socket() error\n");
    
    //listen()转换成服务端socket
    if(listen(serv_sock, 5) == -1)
        error_handling("listen() error\n");
    
    //迭代接收客户端连接
    clnt_adr_sz = sizeof(clnt_addr);
    for(i = 0; i < 5; i++)
    {
        //accept()接收连接请求
        clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_adr_sz);
        if(clnt_sock == -1)
            error_handling("accept() error\n");
        else
            printf("Connected client %d \n", i + 1);
        
        //用fdopen函数使用标准I/O
        readfp = fdopen(clnt_sock, "r");
        writefp = fdopen(clnt_sock, "w");
        while(!feof(readfp))
        {
            fgets(message, BUF_SIZE, readfp);
            fputs(message, writefp);
            fflush(writefp);//快速刷新标准输出缓冲区
        }
        fclose(readfp);
        fclose(writefp);
    }
    close(serv_sock);
    return 0;
}

void error_handling(char* message)
{
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(-1);
}
